The monitoring of movements of monitored individuals involves a variety of sectors, including parolees and home confinement. The technology has its roots in the home arrest systems of the 1980's, in which a user wearable component—typically a “beacon” anklet that was locked to the monitored person, would communicate wirelessly with a stationary base unit. The range was limited to a few feet of the radio frequency transmitter and receiver. The base unit included a telephone connection for communicating with the authorities. If the monitored person left the short range allowed by the equipment, the tag and the base unit would lose contact and the base unit would respond by sending an alert to the authorities.
A later generation of the technology incorporated GPS and cellular telephone technology in a locked anklet. The device would actively monitor the location of the monitored person over time and transmit the data to a central monitoring location (e.g., police or parole monitoring services). The central location could store and analyze the data for prohibited movements (e.g., a sex offender near a school) or cross reference the movement data with crime data to see if the monitored person was near the crime at the time of the crime. U.S. Pat. Nos. 5,867,103, 6,160,481, 6,218,945, 6,512,456 and 6,703,936, incorporated herein by reference in their entireties, are exemplary of such a system.
A later generation of the technology hybridized the beacon technology and the GPS technology. The system included both an anklet with GPS and cellular communications, along with a short range modem. A fixed base unit at a fixed location (typically the monitored person's residence) could communicate with the ankle when within range of the short range modem. When the anklet was remote from the fixed location, the anklet could operate independently and communicate with the central monitoring location. When it was within range of the fixed location, the anklet could cooperate with the fixed unit. For example, the anklet could discontinue use of its cellular modem in favor of lower power communication with the fixed unit; the fixed unit could then relay the information to the central monitoring location through wired or wireless communication. U.S. Pat. No. 8,334,769, incorporated herein by reference in its entirety, is exemplary of such a system.
Alcohol and substance abuse monitoring has been incorporated into the anklet. Since the anklet worn about the ankle is not accessible by mouth to conduct breathalyzer tests, various technologies monitor the presence of prohibited substances in the sweat of the skin. These technologies are not as effective as breathalyzer tests, as there can be a delay between consumption of a prohibited substance and appearance of the substance in the sweat. Physical obstacles (e.g., a sock) or other chemical skin treatments could interfere with skin based detection and/or require dedicated countermeasures.